\begin{tabular}{@{}c@{}}
\begin{tabular}{l*{7}{c}}
\toprule
& \multicolumn{7}{c}{\textbf{Overall Index}}\\
\cmidrule(lr){2-8} & & \makecell{X=Sleep \\ Duration} & \makecell{X=Sleep \\ Efficiency} & \makecell{X=Baseline \\ Outcome} & \makecell{X=Baseline \\ Naps} & \makecell{X=Female} & \makecell{X=Age} \\
& (1) & (2) & (3) & (4) & (5) & (6) & (7) \\
\midrule
Night-Sleep Treatments & -0.01 & 0.01 & -0.00 & 0.06 & 0.08 & 0.02 & -0.08\\
& (0.04) & (0.06) & (0.05) & (0.05) & (0.07) & (0.07) & (0.06)\\
\addlinespace
X & & 0.14* & 0.06 & 0.57*** & 0.07 & -0.02 & -0.07\\
& & (0.08) & (0.08) & (0.09) & (0.07) & (0.08) & (0.08)\\
\addlinespace
Night-Sleep Treatments*X & & -0.05 & -0.02 & -0.08 & -0.12 & -0.04 & 0.13\\
& & (0.08) & (0.08) & (0.09) & (0.08) & (0.08) & (0.08)\\
\addlinespace
Nap Treatment & 0.12*** & 0.16*** & 0.12** & 0.05 & 0.11 & 0.19*** & 0.12**\\
& (0.04) & (0.05) & (0.05) & (0.05) & (0.07) & (0.07) & (0.05)\\
\addlinespace
Nap Treatment*X & & -0.08 & -0.00 & 0.11 & 0.02 & -0.11 & -0.00\\
& & (0.08) & (0.08) & (0.09) & (0.08) & (0.08) & (0.08)\\
\addlinespace
\midrule
 Participants & 452 & 452 & 452 & 452 & 452 & 452 & 452\\
\bottomrule
\end{tabular}
\end{tabular}
